System and method for electrostatic alignment and surface assembly of photonic crystals for dynamic color exhibition

ABSTRACT

A system and method are disclosed of electrostatic alignment and surface assembly of photonic crystals for dynamic color exhibition. The method includes aligning a plurality of photonic crystal chains in a solution to exhibit color.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Pat. Application No. 16/791,244 filed on Feb. 14, 2020, which claims the benefit of U.S. Provisional Application No. 62/807,000, filed Feb. 18, 2019, which is incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present disclosure generally relates to a method and system for electrostatic alignment and surface assembly of photonic crystals for dynamic color exhibition.

BACKGROUND OF THE INVENTION

Photonic crystals are a class of materials that possess structural color properties and exhibit different colors when geometrically aligned and orientated. Commonly, self-assembled layers of spherical particles form three-dimensional (3D) structures, which diffract light to exhibit color. Due to the mechanism of producing color by photonic crystals, the photonic crystals are inherently angularly dependent and therefore it is important to control the structure and geometry of the photonic crystals.

Controlling the exhibited color of photonic crystals has been completed in two ways. The first and most common method is to change the size of the particles or voids, which are responsible for diffraction. This is often demonstrated through manipulation of the chemical environment of the photonic crystal such that the crystal swells or shrinks and thus exhibits various colors. Applications of this mechanism often fall under a broad category of chemical sensors. Though chemical sensing is important, the same mechanism has limited applicability due to the same chemical sensitivity of the photonic crystals.

More recent advances in control over photonic crystal geometries focus around using remote energies such as magnetic fields to arrange and manipulate the photonic crystal structures. The ability to manipulate the color of the photonic crystal without changing the chemical environment expands the range of the applications photonic crystals may be used.

Manipulating materials with magnetic fields is one example of remote control, but infrastructure to accomplish efficient magnetic control on a scaled down device such as a microdevice is limited in scope. Electric fields, however, have been developed far more substantially providing more infrastructure support to new electric charge based technologies compared with magnetic ones.

Electrophoretic deposition is a common method used to deposit a charged material onto an oppositely charged surface. Electrophoretic deposition is mainly concerned with the simple deposition of material onto a substrate, though it has been shown that anisotropic materials such as nanorods can have an ordered deposition profile and be aligned onto the surface due to an electric dipole on the particles. This ordering has been demonstrated using semiconducting CdSe nanorods and further applied for semiconductor applications such as a thin film lasers. This technique though, has not been applied to or used with photonic crystal materials.

To date, photonic crystals uses are advertised as the next generation of tunable colors and pigments, but have been used for little more than chemical, pressure, and magnetic field sensors, which have limited use in industry. Magnetic field control has enabled remote manipulation of photonic crystals. However, the engineering infrastructure needed to support magnetic applications also must be evolved in order to expand applicability of magnetic manipulation. Additional methods of controlling photonic crystal structures and their geometry is important to capitalizing on their unique color exhibiting properties and employing them across a wider range of applications for industry and consumer goods. Much of industry has evolved around electricity and electric fields. By creating photonic crystals that can be manipulated electrically, the photonic crystals can be adapted to existing industrial infrastructure to better support the use of photonic crystals in a broader set of applications.

SUMMARY OF THE INVENTION

In consideration of the above issues, it would be desirable to have a system and method for electrostatic alignment and surface assembly of photonic crystals for dynamic color exhibition.

A method is disclosed of electrostatic alignment and surface assembly of photonic crystals for dynamic color exhibition, the method comprising: dispersing a plurality of photonic crystal chains into a solution; placing the solution of the plurality of photonic crystal chains in a container (i.e., an apparatus, device, means and the like that contains or holds the solution comprising a plurality of photonic crystal chains); and assembling and aligning the plurality of photonic crystal chains in the solution by a local charge build up on a surface of the container to exhibit color.

A system is disclosed for dynamic color exhibition, the system comprising: a plurality of photonic crystal chains dispersed into a solution; a container, the container containing the plurality of photonic crystal chains in the solution; and wherein the plurality of photonic crystal chains in the solution assemble and align exhibiting color when a local charge build up is placed or located on or near a surface of the container.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1A is an illustration of a solution of electrically sensitive photonic crystal chains having a random distribution in accordance with an exemplary embodiment.

FIG. 1B is an illustration of an assembly and alignment of photonic crystal chains diffracting a specific color in the presence of a local charge build up on a surface of a container.

FIG. 2A is an illustrations of orange photonic crystal chains with a blue background dye in a polycarbonate cuvette, wherein the orange color is due to the assembly and alignment of the photonic chains in a region of charge build up on the containers surface from rubbing with the tip of a finger (left) and no stimuli (right).

FIG. 2B is an illustration of yellow-green photonic crystal chains with a red background dye sensing a localized charge build up on the wall of a polypropylene container.

DETAILED DESCRIPTION

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

The disclosure consists of photonic crystals which are sensitive to electric charge on a surface such that the photonic crystals may self-assemble or align onto said surface and exhibit color. In accordance with an exemplary embodiment, hydrophobic silica coated nanomaterials retain latent charges on their surfaces when dispersed into non-polar solvents. In accordance with an exemplary embodiment, these latent charges tend to accumulate on sharp edges, in this case the ends/tips of the one-dimensional (1D) geometries of these particles which in turn create electric dipoles at those ends of the anisotropic nanomaterials. These electric dipoles on the nanoparticles impart a sensitivity to other charges or charge potentials that may be present. Hence, when an electric field is applied through solution or built up on the wall of the container, the anisotropic nanoparticles align and self-assemble in the charged region. Because these materials are photonic crystals, when aligned or self-assembled, these materials exhibit color by diffraction.

In accordance with an exemplary embodiment, this phenomenon of using photonic crystals as disclosed can be used for viewing, measuring, and sensing charge build-up on surfaces, which can be an added tool to reduce risks in industry where electrically sensitive equipment or highly flammable fuels are used and where static discharges can become dangerous. In accordance with an exemplary embodiment, the disclosure can also be employed to manipulate photonic crystals near a surface or in solution allowing for novel reflective display technologies using photonic crystals having the support of an established electronic device infrastructure.

In accordance with an exemplary embodiment, the disclosure described here uses hydrophobic photonic crystals to exhibit a color when self-assembled and aligned onto a charged surface. Specifically Fe₃O₄ nanoclusters are arranged into one-dimensional (1D) chains and fixed by a coating of SiO₂ to form a linear pea-pod like structure which is made hydrophobic by functionalizing the silica surface with octadecyltrimethoxysilane (ODTMS). Hydrophobic surface treatment can be accomplished using various other moieties, such as linear alkane silanes (beyond the exemplified octadecyl), branched alkane silanes, halogenated silanes, and other moieties known in the art. In accordance with an exemplary embodiment, control over the size and cluster spacing in the chain allows for color tuning/selection of the photonic crystal. Once hydrophobic, the photonic crystals can be dispersed in a nonpolar solvent to create an electrically sensitive photonic crystal solution. Charge control agents and additional dispersants can be added to the solution in order to tune the behavior or sensitivity of the photonic crystals to the presence of an electric field or surface charges. In accordance with an exemplary embodiment, instead of (1D) chains, anisotropic nanorods or pre-fixed 3D nanorod-based photonic crystals can also be used, which nanorods can be packaged or encapsulated in various substrates such as encapsulation or solid emulsions.

When in a container such as polypropylene or polycarbonate, a static charge can be built-up on the containers surface by the triboelectric effect. When static charges are deposited onto the surface, the photonic crystals in solution self-assemble and align at the charged region. When aligned, the photonic crystals display their color effectively indicating the charge distribution on the wall of the container or through solution. This mechanism is represented schematically in FIGS. 1A and 1B. FIG. 1A shows a solution of electrically sensitive photonic crystal chains having a random distribution, and FIG. 1B illustrates an assembly and alignment of photonic crystal chains diffracting a specific color in the presence of a local charge build up on the surface of the container.

In accordance with an exemplary embodiment, the contrast between the color of the photonic crystal being displayed in a charged region and the background can be improved by the addition of dyes or pigments. Because the photonic crystals align at the surface, the dye in solution will act as a backdrop color without attenuation or interference between the light source and the photonic crystal. FIGS. 2A and 2B show photonic crystal chains sensing the presence of a localized charge build up on the wall of their containers and having an added background dye to improve contrast of the diffraction color in the charged region.

FIG. 2A illustrates orange photonic crystal chains with a blue background dye in a polycarbonate cuvette. The orange color is due to the assembly and alignment of the photonic chains in a region of charge build up on the containers surface by rubbing with the tip of a finger. FIG. 2B illustrates yellow-green photonic crystal chains with a red background dye sensing a localized charge build up on the wall of a polypropylene container.

Methods

Silica surface of Fe₃O₄@SiO₂ photonic crystals are functionalized with octadecyltrimethoxysilane (ODTMS) by dispersing in a mixture of 12.5 mL ethanol and 0.5 mL 28-30% ammonium hydroxide solution in a sealed glass vial. 150uL ODTMS is added while stirring and the temperature is raised to a reflux for 1.5 hours with occasional sonication. In accordance with an exemplary embodiment, the hydrophobic phonic crystals (HPCs) are magnetically separated and washed with hexanes and suspended in non-polar alkane solvents such as hexanes or paraffin oil.

In accordance with an exemplary embodiment, the present disclosure represents an ability to visualize surface charge accumulation and localization on surfaces indicated by a color change.

In accordance with an exemplary embodiment, the electrostatic sensing by photonic crystal chains, that is, surface alignment of nanochains from solution onto the surface of clear plastics or polymers (e.g., polypropylene, polycarbonate) is performed using the triboelectric effect. In accordance with an exemplary embodiment, instead of nanochains, nanorods can be used.

In accordance with an exemplary embodiment, the nanorods can be anisotropic nanorods or pre-fixed 3D nanorod based photonic crystals, which can be packaged or encapsulated in various substrates such as encapsulation or solid emulsions.

As used herein, an element or step recited in the singular and preceded by the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “example embodiment” or “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional examples that also incorporate the recited features.

The patent claims at the end of this document are not intended to be construed under 35 U.S.C. §112(f) unless traditional means-plus-function language is expressly recited, such as “means for” or “step for” language being expressly recited in the claim(s).

It will be apparent to those skilled in the art that various modifications and variation can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents. 

What is claimed is:
 1. A method for dynamic color exhibition comprising: aligning a plurality of photonic crystal chains in a solution to exhibit color. 